The present invention relates in general to inflight refueling devices for aircraft, commonly known as drogues. In particular, the present invention relates to an air refueling drogue that is attached to a fuel hose and deployed rearwardly from the storage pod of a tanker aircraft to provide a bell shaped, stable target for a receiving aircraft in need of fuel.
Many long endurance missions require that aircraft have to be refueled in the air (literally on the fly). Such an operation requires a tanker aircraft and a means for transferring fuel from the tanker aircraft to the receiving aircraft. One widely used method for conducting such an operation includes the inflight deployment of a drogue and fuel transfer hose from a tanker aircraft into the airstream.
The tanker aircraft has a refueling pod attached to it. In the pod is a reel arrangement which holds a fuel hose, typically fifty feet in length. Attached to the end of the fuel hose is a valving device called a coupling and a drag/target device called a drogue. The drogue is stored in the rear part of the refueling tanker pod. When a receiving aircraft requires refueling, the drogue is ejected by a spring from the back of the pod into the airstream. After clearing the back of the pod, aerodynamic forces acting on the drogue are used to set up the final deployment of the system.
The aerodynamic drag on the drogue pulls the refueling hose and coupling out of the pod. The aerodynamic drag provides the major force to unreel the fuel hose and also provides the resistive force for the receiving aircraft probe. A probe in the receiving aircraft is then brought into alignment with the drogue and forcibly inserted and locked into a coupling device located at the center of the drogue. The probe on the receiving aircraft has to overcome the coupling valve and latching forces. The probe must be fully locked in place before fuel is transferred between the tanker and the receiving aircraft. The drogue also produces aerodynamic stabilizing by providing damping forces on the refueling system.
Although drogues have worked effectively for many years, there are many inadequacies. Prior drogues are complex, employing over 780 metal parts and a fabric ring parachute. A single failure can be disastrous and become xe2x80x9cforeign object damagexe2x80x9d (FOD) if ingested by the receiving aircraft jet engine. In addition, prior drogues are costly to build, repair and maintain. Sometimes the probe on the receiving aircraft can become entangled or even pierce the fabric canopy on prior drogues thereby damaging the drogue assembly and preventing the refueling operation. In addition, the drogue must be small enough to be easily stored in the storage pod of the tanker aircraft yet be large enough when deployed to allow the pilot of the receiving aircraft to insert and lock the refueling probe.
It is therefore desirable that a drogue have a minimum number of parts to reduce FOD potential. It is also desirable that a drogue be of a design that results in a minimal cost to build, repair and maintain. At the same time, it is desirable that a drogue be collapsible for the purpose of storage and expandable for the purpose of presenting a large target. It is also desirable that the drogue be durable to withstand repeated altercations with the probe of the receiving aircraft.
It is an object of the present invention to provide a drogue that will have minimum FOD potential.
It is a further object of the present invention to provide a drogue that will be inexpensive to build, repair and maintain.
It is another object of the present invention to provide a drogue that will fly in a predictable stable manner.
It is still another object of the present invention to provide a drogue that will easily open up when ejected into the airstream and easily collapse when withdrawn back into the storage pod.
It is also an object of the present invention to provide a durable drogue that can withstand repeated altercations with a refueling probe.
The present invention provides a refueling drogue for rearward deployment from a tanker aircraft into an air stream, comprising a fuel valve for receiving fuel from the tanker aircraft and controlling a flow of the fuel; a coupling attached to the fuel valve for receiving fuel from the fuel valve; and a plurality of struts, each strut having a proximal end and a distal end wherein each strut is rotatably connected to the coupling at the proximal end and each strut includes a winglet at the distal end.
Preferably, each strut includes an opening at the distal end, the refueling drogue further comprising a cord disposed in the opening at the distal end of each strut thereby limiting expansion of the plurality of struts.
The refueling drogue further comprises a ring assembly for attaching the plurality of struts to the coupling wherein each strut includes a second opening at the proximal end for attaching the strut to the ring assembly.
In a preferred embodiment, each strut and winglet are integrally molded from a high molecular weight plastic material.
The plurality of struts preferably comprises a set of long struts and a set of short struts. The long and short struts are connected in an alternating manner to the coupling. Winglets on the long struts are wider than winglets on the short struts.
In one embodiment, each strut includes an internal surface configured such that the plurality of struts provides a substantially bell-shaped opening. Further, each strut includes an external surface and two side surfaces, a surface area of the side surfaces being substantially greater than a surface area of the internal and external surfaces.
Further objects, features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the following drawing.